Recently, VCRs have been made smaller and smaller, and camcorders, in particular, have been remarkably downsized. This market tendency and the recent advanced technique require a fine control over tape tension when the tape is supplied or taken up.
The construction and operation of a conventional reel stand mounted to this kind of apparatuses is described with reference to FIGS. 5 and 6.
The conventional reel stand, in general, has a contact member comprising a brake-pad made of resin or felt. The brake-pad urges an outer rim of the reel stand to apply some load thereto in order to provide tape tension.
FIG. 5 is a plan view of the conventional reel stand. FIG. 6 is a cross section of the reel stand shown in FIG. 5.
In FIG. 6, reel-stand-supporting-shaft 513 is fixedly secured to chassis 516. The reel stand comprises reel base 503, spring 504, reel stopper 505, brake contact section 506, yoke plate 507, magnet 508, washer 509, clutch gear 510, panel 511, reel cap 512, direct-coupled gear 514 and rotation-sensing-target 515. The reel stand is journaled by shaft 513. Rotating force of an outer gear (not shown) travels through clutch gear 510 or direct-coupled gear 514 to drive the reel stand. Then, reel "1a" within a cassette case "1b" mounted on the reel stand is spun via reel stopper 505.
Reel base 503 is journaled by shaft 513 and receives reel "1a" thereon. Reel stopper 505 allows reel "1a" to arbitrarily move in axial direction but engages reel "1a" in the rotational direction. Compression spring 504 always urges reel stopper 505 upward from reel base 503. Reel cap 512 is screwed (the screw is not shown) on reel base 503 and prevents stopper 505 from coming off. Reel cap 512 contacts a tip of shaft 513 so that the entire reel stand is supported by the shaft in the thrust direction. Reel base 503, yoke plate 507 and brake contact section 506 are integrally assembled. Brake contact section 506 made of resin contacts brake pad 501 mounted to brake 502 disposed outside the stand, thereby applying some load to the rotation of the reel stand. Magnet 508 attracts yoke plate 507 with its own magnetic force, and rotates with yoke plate 507.
Clutch gear 510 is integrally assembled with panel 511 made of hysteretic material, and contacts reel base 503 via washer 509. Clutch gear 510 is coaxial with reel base 503 and can rotate arbitrarily. Panel 511 is attracted by magnet 508 due to the rotation of gear 510, and transfers the rotation to reel base 503. The clutch mechanism is thus structured.
Direct-coupled gear 514 is press-fitted into reel base 503 and integrated therein. Rotation-sensing-target 515 is disposed on the bottom face of the reel stand to face a rotation detector (not shown) mounted to chassis 516. This set of detector and target 515 can detect the rotation of the reel stand.
Another shaft 517 is fixedly mounted on chassis 516. In FIG. 6, brake 502 is mounted to shaft 517 and hits break contact section 506 by spring action. Brake pad 501, shaped as a plate and made of resin, is stuck to brake 502, and is urged to brake contact section 506 by twisted spring 518.
A braking operation of the conventional reel stand discussed above is described hereinafter.
The rotating force of an outer driving gear (not shown) travels through clutch gear 510 or direct-coupled gear 514 to rotate the reel stand. In this case, if little hold-back load were applied, reel "1a" situated on the reel stand would be rotated and tape wound on reel "1a" would be loosened. In order to overcome this problem, light hold-back load must be applied with the reel stand by contacting brake pad 501 to brake contact section 506 of the reel stand. This braking operation always functions as hold-back torque to the reel stand both in recording mode and play-back mode.
As such, the conventional reel stand requires a space outside thereof for accommodating the brake mechanism including brake 502, brake pad 501, shaft 517 and spring 518. This space requirement has restricted the apparatus from being further downsized. Further, the outer rim of the reel stand contacts the brake, and the peripheral velocity of brake contact section 506 is so high, which generates a great amount of frictional heat between section 506 and pad 501, and both are worn out in a short period of time due to the friction.